JPH0735897B2 - How to control the temperature of the water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a plurality of gas burners as a heating burner for a water tube type water heating heat exchanger, and proportionally adjusts a fuel gas supply flow rate to these gas burners. Valve, and a switching valve that switches the number of gas burners that supply fuel gas, so that the hot water supply capacity can be proportionally controlled over a wide range by combining fuel gas supply flow rate adjustment with a proportional valve and switching the number of ignition burners with a switching valve. The present invention relates to a method for controlling a hot water supply temperature of a water heater having a temperature control device having the above structure.

[Conventional technology]

FIG. 5 is a schematic sectional view showing a gas water heater provided with this type of temperature control device.

Reference numeral 1 denotes a water heater main body, in which a plurality of gas burners 2, a manifold 3 having nozzles for supplying fuel gas to the gas burners, and a water pipe type heat exchanger 4 for heating water.
And are provided.

The water supply is supplied from the water supply pipe 5, and is distributed to the heat exchanger 4 via the flow sensor 6, the water supply temperature sensor 7, and the water temperature detection water amount control device 8.

On the other hand, the fuel gas is supplied from the gas pipe 9, the solenoid valve 10,
It is supplied to each of the plurality of gas burners 2 through the proportional valve 11 and the manifold 3. A switching valve 17 is provided in the manifold 3, and when the switching valve 17 is closed, as shown in FIG. 6, the fuel gas supply to the gas burner 2 in the right half of the figure is cut off to extinguish the fire. Then, only the gas burner 2 in the left half of the figure is burned.

Combustion air flows in from the air supply pipe 13 as shown by arrows c and c ', and flows as shown by arrows d and d'to perform a combustion reaction, and the combustion fan 12
And is discharged from the exhaust pipe 14 as indicated by arrow e.

Hot water tap 16 through the hot water supply hot water supply pipe 15 heated by the heat exchanger 4
Is supplied to. The hot water supply pipe 15 is provided with a hot water supply temperature sensor 18.

Thus, a plurality of gas burners 2 are provided as heating burners for the water tube type water heating heat exchanger 4, and the proportional valve 11 for adjusting the flow rate of the fuel gas supplied to these gas burners 2 and the A fuel control device for a water heater, which is provided on the downstream side of the proportional valve 11 and has a switching valve 17 for switching the number of gas burners 2 to be used, is controlled by a microcomputer (not shown), and the temperature and flow rate of the water supplied to the microcomputer are controlled. , Proportional control is performed over a wide temperature range by a combination of the opening adjustment of the proportional valve 11 and the open / close control of the switching valve 17 based on the hot water temperature and the set temperature instructed by the user.

As a technical problem in wide-range proportional control by such a method, there is a problem of continuity of characteristic curves. That is,
Opening / closing control of the proportional valve 11 is continuously and steplessly performed, but switching of the number of gas burners to be used by the switching valve 17 is performed stepwise. Therefore, the relationship between the manipulated variable and the number (heating capacity) becomes discontinuous before and after the switching valve 17 is opened and closed.

More specifically, when the proportional valve is operated in the direction of increasing the opening thereof, when the opening of the proportional valve reaches a predetermined opening and the switching valve is opened, the hot water temperature suddenly changes suddenly. On the contrary, when the proportional valve is operated in a direction to decrease the opening degree and reaches a predetermined opening degree different from the above and the switching valve is closed, the hot water outlet temperature temporarily changes suddenly.

In this way, in order to prevent the problem that the rate of change in the outlet water temperature changes suddenly with the opening and closing of the switching valve,
The technique described in No. 63-30031 “Proportional control type gas water heater” is known. In this invention, a correction circuit is connected between the proportional valve mechanism and the switching valve mechanism to suppress a change in the total amount of the fuel gas supply flow rate when the switching valve is opened and closed.

FIG. 2B is a chart showing an example of the control characteristics in the above-mentioned known technique.

The horizontal axis represents the manipulated variable y. This manipulated variable is directly proportional to the proportional valve opening and also to the proportional valve current. The vertical axis represents the fuel gas supply flow rate by the number of water heaters.

Curve BB 'represents the time when the entire gas burner is used, that is, the switching valve is opened, and curve A
-A 'is when only part of the gas burner is used,
That is, it represents the time when the switching valve is closed. In this known example, the heating capacity at the point B'representing the maximum heating capacity is 16, and the proportional valve current value at this point B'is about 200 mA.
Is. The heating capacity at point A, which represents the minimum heating capacity, is No. 4.

In this known example, when the proportional valve is gradually opened with the switching valve closed, the control state on the chart shown in FIG. 2 (B) moves from point A to point A '. Then, when the point a of the predetermined opening is reached, the switching valve is opened and shifts to the point b on the curve BB ′, but at this time, the proportional valve is closed by the angle θ _a by the correction circuit and the burner used. The increase in the fuel gas supply flow rate due to the increase in the number is offset. In this way, the arrow arrow becomes horizontal, and the switching valve is opened without change in the number so that all gas burners can be used.

Similarly, when the proportional valve is gradually closed while the switching valve is opened, the control valve moves from the control state point B ′ toward the point B, and has a predetermined opening degree different from the above-mentioned predetermined opening point a. When the point _c is reached, the switching valve is closed and the proportional valve is opened by the angle θ _{a, and the} curve moves horizontally to the point d on the curve A-A ′ (without a change in the number) as indicated by the arrow hani.

In this way, the increase / decrease in the supply gas flow rate due to the opening / closing operation of the switching valve is offset by the correction of the proportional valve opening, and the number immediately before and after the switching opening / closing operation are equalized. I am enthusiastic. That is, the flow rate of the supply gas immediately before and after the switching valve opening / closing operation is equalized.

[Problems to be Solved by the Invention]

According to the above-mentioned known technique, as described with reference to FIG. 2 (B), the supply gas flow rate hardly changes immediately before and after the opening / closing operation of the switching valve. That is, the amount of heat generated by combustion hardly changes.

However, since the heat exchanger 4 has a heat capacity, there is a problem in that the hot water temperature changes suddenly temporarily due to heat storage and heat dissipation of the heat exchanger 4 as the number of gas burners used is switched.

Now, it is assumed that the switching valve 17 is closed and the gas burner 2 in the right half of the figure is at rest as shown in FIG. In this state, the left half part 4a of the heat exchanger 4 is heated to raise the temperature, and the right half part 4b is heated.
Is relatively cold. In this state, when the switching valves 17 are opened and all the bavana 2 are ignited as shown in FIG. 5, the right half portion 4b of the heat exchanger 4 in the figure still rises in temperature to reach thermal equilibrium immediately after the ignition. Not reach In this state, the feed water flows through the unheated portion 4b, which is located upstream of the heat exchanger 4, and is then heated by the heated portion 4a. For this reason, the effect of the ignition of the gas burner 2 in the right half of the drawing is slightly delayed.

When the flow rate of hot water discharged from the water heater at a certain set temperature T _sp is gradually increased, the proportional valve 11 is gradually opened accordingly. FIG. 7 shows changes in the hot water outlet temperature when the switching valve 17 is opened after reaching the predetermined opening. The reason why the hot water outlet temperature shows a remarkable drop D temporarily is that the heat is absorbed by the unheated portion (the portion which has been stopped until then) 4b of the heat exchanger.

Similarly, when the hot water discharge amount is reduced and the switching valve is closed, heat is radiated from the preheated portion 4b of the heat exchanger 4, causing a temporary rise U in the hot water discharge temperature as shown in FIG.

The present invention has been made in view of the above circumstances, and provides a control method that can improve control characteristics in a temperature control device of a water heater to remarkably suppress fluctuations in hot water temperature due to opening / closing operation of a switching valve. The purpose is to do.

[Means for Solving the Problems]

Next, with reference to FIG. 2 (A) corresponding to the control characteristic in one embodiment of the temperature control method according to the present invention, a known example (second
The description will be made in contrast with FIG.

In the known example (FIG. 2 (B)), the switching valve is opened and the proportional valve is closed by the angle θ _a, so that the curve A-
A horizontal transition (without a change in the number) is made from a point A on A'to a point B on the curve BB 'as shown by an arrow I.
In the figure (A)), the transition is made from the point e on the curve A-A 'to the point on the curve BB' while increasing (the number increases).

That is, as compared with the point e indicating the control state immediately before the switching valve is opened, the point indicating the control state immediately after the opening is positioned above and the number thereof is increased.

Similarly, as compared with the point g immediately before the switching valve is closed, the point g immediately after the switching valve is positioned below and the number thereof is reduced.

[Action]

As in the known example (FIG. 2 (B)), heat is generated when the number immediately after the switching valve is opened (b) is equal to that when the switching valve is opened (the fuel gas supply flow rate is the same), as compared to immediately before the switching valve is opened (b). Due to the heat absorption of the unheated part of the exchanger, the tap water temperature temporarily drops (Fig. 7).
However, if the number is increased when the switching valve is opened as in the present invention (FIG. 2 (A)), the amount of heat generated by combustion is compensated for by the amount of heat generated by combustion, and therefore the switching valve is opened. Temporary drop in the hot water temperature due to is prevented (or reduced).

Further, since the number becomes smaller as the switching valve is closed, a temporary rise (or a slight lightening) in the outlet heated water temperature due to heat radiation from the already heated portion of the heat exchanger is prevented.

〔Example〕

FIG. 2A is a control characteristic chart in one embodiment of the temperature control method according to the present invention.

This embodiment is an improvement in which the present invention is applied to a control method of a known example showing the control characteristic shown in FIG. 2 (B), in which the horizontal axis, the vertical axis scale, and the switching valve state Curve A
-A 'and the curve BB' in the open state of the switching valve are the same as in the above-mentioned known example.

In this example (FIG. 2 (A)), the manipulated variable y (proportional valve current,
When the value (proportional to the proportional valve opening) gradually increases and reaches the manipulated variable a corresponding to the predetermined opening, the switching valve automatically opens.

The control state immediately before the switching valve is opened is curve A-
It is the point e on A '. The horizontal axis coordinate value of this point e is the above-mentioned a, and the vertical axis coordinate value thereof represents the number immediately before the switching valve is opened.

Simultaneously with the opening of the switching valve, a correction mechanism (not shown) is activated to close the proportional valve by θ _b, the manipulated variable becomes a ′, and the control state shifts to a point on the curve BB ′.

The number (vertical axis coordinate value) of the point is set higher than the number (vertical axis coordinate value) of the point e.

As a result, in comparison with the known example (FIG. 2 (B)), which has a horizontal arrow arrow indicating the change in the control state when the switching valve is opened, the present embodiment (FIG. 2 (A)). The arrow point of is diagonally upward.

In the known example, when the switching valve was opened, there was a temporary decrease D in outlet heated water temperature as shown in FIG. 7, but in this example, the number increases with the opening of the switching valve. As shown in Fig. 3, the change in the tap water temperature is small, and the user does not feel uncomfortable.

When the manipulated variable changes while the switching valve is open, the control state moves on the curve BB '. When the operation amount is reduced to reach the predetermined opening b, automatically with the switching valve is closed proportional valve angle theta _{b 'only} open operation amount b', and the control state is the curve B-B ' Transition from the upper point G to the point A on the curve A-A '.

Compared with the point g immediately before the closing of the on-off valve, the point g immediately after the valve closing is set to have a smaller number. For this reason, in the known example, the hot water outlet temperature rise U when the switching valve is closed as shown in FIG. 8, but in this example, the temperature change is small as shown in FIG. 4, and the user feels uncomfortable. Don't give.

FIG. 1 is a flow chart of an example in which the control method according to the present invention is automatically performed by a microcomputer.

When it starts in flow 4a, ignition is detected in flow 4b.

When it is judged that y ≧ a in the flow 4c, the switching valve 17 (see FIG. 5,
(See FIG. 6) is opened (flow 4d), and the manipulated variable y immediately after the switching valve 17 is opened is corrected so that y ≧ a ′ (flow 4e).

After the switching valve is opened in this way, in flow 4f, y <
If it is judged to be b, the switching valve 17 is closed (Flow 4
g), the manipulated variable y immediately after the switching valve 17 is closed is corrected so that y ≦ b ′ (flow 4h).

[Effects of the Invention] As described above, when using the temperature control device for a water heater which is provided with the proportional valve and the switching valve and performs the proportional control over a wide range, the control method according to the present invention is applied to the switching valve. If the control is performed so that the number immediately after the valve is opened is larger than the number immediately before the valve is opened, and the number immediately after the valve is closed is smaller than the number immediately before the switching valve is closed, It is possible to remarkably reduce the temporary fluctuation of the tap water temperature due to the opening and closing operations of the valve.

[Brief description of drawings]

FIG. 1 is a flow chart in one embodiment of the control method according to the present invention. FIG. 2 is a chart showing the temperature control characteristics of the water heater, FIG. 2 (A) showing the control characteristics in the above embodiment, and FIG. 2 (B) showing the control characteristics of the known example. FIG. 3 and FIG. 4 are charts showing changes in hot water outlet temperature when the switching valve is opened and closed in the above embodiment. 5 and 6 are schematic views of a water heater equipped with a temperature control device having a proportional valve and a switching valve, FIG. 5 shows a state in which the switching valve is open, and FIG. 6 shows switching. It depicts the valve closed. FIG. 7 and FIG. 8 are charts showing changes in hot water outlet temperature due to switching valve opening / closing operation, for explaining problems in the control technique according to the known example. 1 ... Water heater main body, 2 ... Gas burner, 3 ... Manifold, 4 ... Heat exchanger, 5 ... Water supply pipe, 9 ... Gas pipe,
11 …… Proportional valve, 17 …… Switching valve.

Claims (1)

[Claims] 1. A proportional valve for controlling a gas flow rate to be supplied to a plurality of gas burners, and a switching valve provided downstream of the proportional valve for shutting off gas supply to a part of the gas burners in the plurality of gas burners. , When the opening of the proportional valve becomes larger than the predetermined opening, the switching valve is opened and all the gas burners are ignited. When the opening of the proportional valve becomes smaller than the predetermined opening different from the above, the switching valve is closed. In the method of controlling the hot water outlet temperature of a water heater equipped with a temperature control device that extinguishes the burner of the section, the switching valve is compared with the number immediately before the opening of the proportional valve and the switching valve is opened. Control is performed so that the number immediately after opening is large, and the number immediately after the switching valve is closed compared to the number immediately before the switching valve is closed due to the opening of the proportional valve decreasing. Characterized by controlling to reduce the number Temperature control method of the water heater.